TW202306131A - Ferroelectric tunnel junction with multilevel switching - Google Patents

Abstract

The disclosed and claimed subject matter relates to a ferroelectric tunnel junction that is BEOL compatible having a film comprising crystalline ferroelectric materials that include a mixture of hafnium oxide and zirconium oxide having a substantial (i.e., approximately 40% or more) or majority portion of the material in a ferroelectric phase as deposited (i.e., without the need for further processing, such as a subsequent capping or annealing) and methods for preparing and depositing these materials. An interfacial layer is formed by oxidizing one or more of a first electrode and a second electrode. The FTJ has a memory window of between about 2X and 10X and is stable over 4 resistance states for at least 10<SP>3</SP>s. The FTJ is produced at temperatures less than or equal to 400 degrees Celsius.

Description

Ferroelectric Tunneling Junction with Multilevel Switching

Cross-reference to related applications

This case claims priority to U.S. Provisional Patent Application Serial No. 63/225,400, filed July 23, 2021, which is hereby incorporated by reference.

The subject matter disclosed and claimed herein relates generally to ferroelectric materials deposited using vapor phase techniques including atomic layer deposition (ALD). More specifically, subject matter disclosed and claimed herein pertains to ferroelectric tunneling junctions (FTJs) having thin-film crystalline ferroelectric materials comprising a substantial portion (i.e., about 40% or more Multiple) mixtures of hafnium oxide and zirconium oxide as ferroelectric phase materials; and methods of preparing and depositing these materials. Apparently, these materials exhibit ferroelectric properties without further treatment, such as subsequent capping or annealing.

Ferroelectric materials based on hafnium oxide and zirconium oxide can be used in various computer devices including non-volatile memory and power-saving logic devices due to their strong nonlinear capacitance and remanent polarization. These materials can also be used in a variety of other thermal and magnetic applications. Materials containing hafnium oxide and zirconium oxide are well suited for these applications due to their compatibility with many CMOS assembly processes and materials. It is also desirable because it can be deposited into thin films from the vapor phase, including by ALD processes and other known processes (e.g., chemical vapor deposition (CVD) ) or pulsed CVD. Materials based on hafnium oxide and zirconium oxide are polymorphic. Therefore, their atoms can be arranged in several crystal structures (i.e., different ordered atomic arrangements). Well-known is the The most stable overall structure of the material is the monoclinic phase; however, this phase does not support ferroelectricity. Other polymorphs (e.g., some orthorhombic and rhombohedral phases) have the required symmetry, while other polymorphs (e.g., the tetragonal phase commonly found in zirconia thin films) can be of the antiferroelectric type. The list of related arts appended hereto identifies the principles that describe these general features and aspects of the art in more detail. reference materials.

In many vapor phase and atomic layer deposition processes for mixed hafnium oxide and zirconium oxide materials, the material is amorphous as deposited.

Even after thermal treatment, crystallization into the monoclinic or other non-ferroelectric phases is common, reducing the proportion of material capable of ferroelectric behavior. Several techniques have been developed to suppress the monoclinic phase in favor of a phase that can support ferroelectricity. For example, it has been reported that other elements, including but not limited to Si, Al, Gd, La, and Y, are incorporated into the material as suppressed monoclinic elements by sequentially or simultaneously introducing their precursors into the gas phase. crystalline means.

A study showed that thick films (about 30 nm) of hafnium oxide and zirconium oxide can exhibit weak ferroelectricity of the ferroelectric phase. See Y. Li et al., "A Ferroelectric Thin Film Transistor Based on Annealing-Free HfZrO Film". It appears that this behavior is due to reduced surface energy effects compared to thinner films and prolonged exposure to heat, which is functionally equivalent to annealing to produce films of this thickness. However, this study acknowledges what is generally known in the art: thin films (approximately 20 nm or smaller) do not exhibit ferroelectric behavior without annealing at elevated temperatures (alone or in combination with doping) and the aforementioned face protection methods.

Thus, obtaining the desired ferroelectric phase has traditionally depended on a complex combination of (i) the deposition conditions of the material itself, (ii) the choice of dopants, interfaces, and importantly the top interface, and (iii) the deposition conditions. post heat treatment. It can be readily appreciated that this combination of factors greatly limits the usefulness of this material in terms of possible substrates, interlayers, electrodes, compositions and processes. Indeed, the heat distribution in devices implementing such ferroelectric materials may not be compatible with all necessary or desired applications in which ferroelectric materials may be useful. For example, it has been observed that specific electrodes may be required to tune the electronic work function, interfaces may be required to create barrier layers to prevent chemical reactions and atomic diffusion, and heat treatment conditions may be affected by stresses introduced in other layers in the multilayer stack limits.

Ferroelectric tunnel junctions (FTJs) are two-terminal memory devices in which ferroelectric material and other interfacial dielectric materials are sandwiched together between two similar/dissimilar electrodes, which store data according to the resistive switching of the device (i.e., low The resistive state and the high resistive state represent two different memory states and thus store one bit of data). The change in resistance is caused by a change in the height of the tunneling barrier between the two electrodes due to the switching of the orientation of the permanent charge dipole in the ferroelectric material. Ferroelectric materials are typically crystalline/polycrystalline materials that form permanent charge dipoles due to asymmetric dipole charge centers within the unit cell that can be switched by applying an electric field. Due to the permanent orientation switching of the dipoles, in the absence of an electric field, this material was shown to change the polarization of the direct tunneling barrier between the two electrodes (remanent magnetic polarization).

Typically, for an FTJ to work, an inherent asymmetry between the two electrodes is required. This asymmetry can be achieved by (i) using two different types of contact materials (two different metals or a metal and a semiconductor) for the two electrodes, (ii) using a non-ferroelectric interfacial dielectric material .

The basic idea of a ferroelectric tunneling junction (FTJ) (then called a polar switch) can be attributed to Esaki et al. and formulated in 1971. The FTJ has been extensively studied in the literature over the past 10 years and several materials such as lead zirconate titanate-Pb(Zr _x Ti _1-x )O ₃ (PZT), bismuth ferrite (BiFeO ₃ - BFO), barium titanate (BaTiO ₃ - BTO), lanthanum strontium manganite (La _0.67 Sr _0.33 MnO ₃ - LSMO), organic polyvinylidene fluoride (PVDF) and organic poly(vinylidene fluoride-trifluoro Ethylene)-P(VDF-TrFE). Due to the poor BEOL process compatibility and integration complexity of these materials, hafnium oxide-based FTJs have recently been intensively studied due to their good compatibility with CMOS processes, especially with certain dopants (Zr, Si) Improves the ferroelectricity of the material. The use of interfacial layers (SiO ₂ , Al ₂ O ₃ , WO _x ) was also recently introduced to introduce asymmetry into the FTJ stack and improve the performance of this memory from the perspective of tunneling resistance (TER) range and retention, but The results are still insufficient to allow more than 2 to 3 memory-level programming to be done with acceptable retention times of more than a few hours.

In a first main aspect, the disclosed subject matter relates to a ferroelectric tunnel junction (FTJ) comprising: a substrate; a first electrode and a second electrode, wherein the first electrode or a portion of the second electrode has been oxidized to form an interfacial layer; a thin film comprising crystalline material comprising hafnium oxide and zirconium oxide disposed between the first electrode and the second electrode, wherein the crystalline material exhibits as-deposited ferroelectricity behavior; and a voltage source connected to the first electrode or the second electrode.

或

其中(i) M係選自Zr及Hf，並且(ii) R ¹、R ²、R ³、R ⁴、R ⁵、R ⁶、R ⁷及R ⁸係各自獨立地選自C ₁-C ₆直鏈烷基、C ₁-C ₆支鏈烷基、C ₁-C ₆鹵代直鏈烷基及C ₁-C ₆鹵代支鏈烷基。在該第一主要態樣之另一態樣中，該結晶材料係衍生自一或更多具有式I或式II的茂金屬前驅物：

或

其中(i) M係選自Zr及Hf，並且(ii) R ¹、R ²、R ³、R ⁴、R ⁵、R ⁶、R ⁷及R ⁸各自獨立地為C ₁-C ₆直鏈烷基。在該第一主要態樣之另一態樣中，該結晶材料係衍生自一或更多具有式I或式II的茂金屬前驅物：

或

其中(i) M係選自Zr及Hf，並且(ii) R ¹、R ²、R ³、R ⁴、R ⁵、R ⁶、R ⁷及R ⁸各自為甲基。在該第一主要態樣之另一態樣中，於極化電場測量時存在磁滯性及剩磁極化。該膜具有約0.2 nm至約10 nm的厚度。在該第一主要態樣之另一態樣中，該膜具有約0.2 nm至約5 nm的厚度。在該第一主要態樣之另一態樣中，該膜具有大於8μC/cm ²的剩磁極化(Pr)或大於16μC/cm ²的總迴路開度(total loop opening)。 In one aspect of the first main aspect, the first electrode and the second electrode are independently selected from TiN, W, Ni, Ru, Pt, and Al. In another aspect of the first principal aspect, the first electrode and the second electrode are independently selected from TiN and W. In another aspect of the first principal aspect, the ferroelectric tunnel junction is switchable between four different resistance states. In another aspect of the first principal aspect, the resistance state remains stable for at least 10 ³ seconds. In another aspect of the first principal aspect, the FTJ has a memory window in the DC domain of between about 1.5 and about 10 times. In another aspect of the first principal aspect, the FTJ has a memory range between about 2X and about 5X. In another aspect of the first principal aspect, the FTJ can exhibit ferroelectric activity. In another aspect of the first principal aspect, the first electrode comprises tungsten and the second electrode comprises titanium nitride. In another aspect of the first principal aspect, less than 50% of the total volume of the crystalline material constitutes a non-ferroelectric phase component. In another aspect of the first principal aspect, less than 40% of the total volume of the crystalline material constitutes a non-ferroelectric phase component. In another aspect of the first major aspect, less than 40% of the total volume of the crystalline material constitutes a monoclinic phase component. In another aspect of the first principal aspect, less than 50% of the total volume of the crystalline material constitutes a monoclinic phase component. In another aspect of the first major aspect, (i) greater than 50% of the total volume of the crystalline material is in the ferroelectric phase; (ii) less than 50% of the total volume of the crystalline material constitutes a non-ferroelectric phase component and (iii) less than 25% of the total volume of the crystalline material constitutes a monoclinic phase component. In another aspect of the first primary aspect, the ratio of hafnium oxide to zirconium oxide is between about 1:3 and about 3:1. In another aspect of the first principal aspect, the crystalline material has a carbon content of less than about 6 atomic percent. In another aspect of the first major aspect, the crystalline material is derived from one or more metallocene precursors having Formula I or Formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently selected from C ₁ -C ₆ Straight chain alkyl, C ₁ -C ₆ branched chain alkyl, C ₁ -C ₆ halogenated straight chain alkyl and C ₁ -C ₆ halogenated branched chain alkyl. In another aspect of the first major aspect, the crystalline material is derived from one or more metallocene precursors having Formula I or Formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a C ₁ -C ₆ straight chain alkyl. In another aspect of the first major aspect, the crystalline material is derived from one or more metallocene precursors having Formula I or Formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each methyl. In another aspect of the first principal aspect, hysteresis and remanent magnetic polarization are present at the time of polarized electric field measurements. The film has a thickness of about 0.2 nm to about 10 nm. In another aspect of the first primary aspect, the film has a thickness from about 0.2 nm to about 5 nm. In another aspect of the first major aspect, the film has a remanent polarization (Pr) greater than 8 μC/cm ² or a total loop opening greater than 16 μC/cm ² .

In a second major aspect, a method of producing a ferroelectric tunnel junction comprising: (i) providing a substrate; (ii) depositing a first electrode on the substrate; (iii) at a deposition temperature depositing a ferroelectric layer on the first electrode, the step of depositing the ferroelectric layer comprising: (a) exposing the first electrode to a first precursor that does not decompose at the deposition temperature; (b) exposing the first electrode to a first precursor that does not decompose at the deposition temperature; exposing the substrate to a first reactive gas; (c) exposing the substrate to a second precursor that does not decompose at the deposition temperature; and (d) exposing the substrate to a second reactive gas, wherein the first one of a precursor and the second precursor comprises zirconium, and the other of the first precursor and the second precursor comprises hafnium; and (iv) depositing a second electrode on the ferroelectric layer superior.

或

其中(i) M係選自Zr及Hf，並且(ii) R ¹、R ²、R ³、R ⁴、R ⁵、R ⁶、R ⁷及R ⁸係各自獨立地選自C ₁-C ₆直鏈烷基、C ₁-C ₆支鏈烷基、C ₁-C ₆鹵代直鏈烷基及C ₁-C ₆鹵代支鏈烷基。 In another aspect of the second main aspect, the step of creating an interfacial layer by oxidizing the first electrode is performed before step (iii). In another aspect of the second main aspect, the first reactive gas and the second reactive gas are each independently a gas containing one or more of oxygen, water, hydrogen peroxide, and nitrous oxide . In another aspect of the second main aspect, the first reactive gas and the second reactive gas are each independently an oxygen-containing gas, an ozone-containing gas, or a water-containing gas. In another aspect of the second primary aspect, the annealing step is performed at a temperature greater than about 350 degrees Celsius. In another aspect of the second primary aspect, none of the process steps occurs at a temperature greater than about 400 degrees Celsius. In another aspect of the second primary aspect, no interfacial layer is deposited between the ferroelectric layer and the first electrode or between the ferroelectric layer and the second electrode. In another aspect of the second primary aspect, the first gas or the second gas comprises ozone delivered at a volume fraction between about 2% and about 50%. In another aspect of the second primary aspect, additionally comprising an ozone pulsing step prior to depositing the second electrode. In another aspect of the second primary aspect, the ozone pulsing step delivers a gas stream comprising between about 2% and about 50% ozone by volume. In another aspect of the second principal aspect, the deposited crystalline material exhibits remanent magnetic polarization without additional heat treatment. In another aspect of the second primary aspect, the deposited crystalline material has a residual magnetic polarization (Pr) greater than 8 μC/cm ² or a total loop opening greater than 16 μC/cm ² . In another aspect of the second main aspect, the first electrode or the second electrode comprises TiN and the interfacial layer comprises _TiOxNy , where x and _y are integers. In another aspect of the second primary aspect, the first electrode comprises tungsten and the second electrode comprises titanium nitride. In another aspect of the second primary aspect, at least one purging step is additionally included. In another aspect of the second primary aspect, the first reactive gas and the second reactive gas are different gases. In another aspect of the second main aspect, the first precursor and the second precursor are each independently a precursor having formula I or formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently selected from C ₁ -C ₆ Straight chain alkyl, C ₁ -C ₆ branched chain alkyl, C ₁ -C ₆ halogenated straight chain alkyl and C ₁ -C ₆ halogenated branched chain alkyl.

或

其中(i) M係選自Zr及Hf，並且(ii) R ¹、R ²、R ³、R ⁴、R ⁵、R ⁶、R ⁷及R ⁸各自獨立地為C ₁-C ₆直鏈烷基。 In another aspect of the second main aspect, the first precursor and the second precursor are each independently a precursor having formula I or formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a C ₁ -C ₆ straight chain alkyl.

或

其中(i) M係選自Zr及Hf，並且(ii) R ¹、R ²、R ³、R ⁴、R ⁵、R ⁶、R ⁷及R ⁸各自為甲基。 In another aspect of the second main aspect, the first precursor and the second precursor are each independently a precursor having formula I or formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each methyl.

In another aspect of the second main aspect, the method includes an ALD process. In another aspect of the second main aspect, the method includes a CVD process. In another aspect of the second primary aspect, the deposition temperature is between about 200 degrees Celsius and less than about 400 degrees Celsius. In another aspect of the second primary aspect, the deposition temperature is between about 265 degrees Celsius and less than about 390 degrees Celsius. In another aspect of the second primary aspect, the deposition temperature is between about 280 and about 380 degrees Celsius. In another aspect of the second primary aspect, the deposition temperature is less than about 30 degrees Celsius. In another aspect of the second principal aspect, the substrate comprises silicon, germanium, group III-V materials, transition metal dichalcogenides, titanium nitride, titanium, tantalum, tantalum nitride, tungsten, platinum , rhodium, molybdenum, cobalt, ruthenium, palladium or their mixtures, or dielectrics such as silicon oxide, silicon nitride, aluminum oxide, titanium oxide. In another aspect of the second primary aspect, the deposited crystalline material has a thickness of about 0.2 nm and about 20 nm.

In a third major aspect, a method of producing a ferroelectric tunnel junction comprising: (i) providing a substrate; (ii) depositing a first electrode on the substrate; (iii) pulsing oxygen and A plasma of ozone to oxidize a portion of the bottom electrode to form an interfacial layer; (iv) depositing a ferroelectric layer on the first electrode at a deposition temperature, the step of depositing the ferroelectric layer comprising: (a) the exposing the first electrode to a first precursor that does not decompose at the deposition temperature; (b) exposing the substrate to a first reactive gas; (c) exposing the substrate to the deposition temperature without decomposing and (d) exposing the substrate to a second reactive gas, wherein one of the first precursor and the second precursor comprises zirconium, and the first precursor and the second The other of the precursors comprises hafnium; and (v) depositing a second electrode on the ferroelectric layer.

In another aspect of the third major aspect, the first reactive gas and the second reactive gas are each independently a gas containing one or more of oxygen, water, hydrogen peroxide, and nitrous oxide . In another aspect of the third major aspect, the first reactive gas and the second reactive gas are each independently an oxygen-containing gas, an ozone-containing gas, or a water-containing gas. In another aspect of the third major aspect, the annealing step is performed at a temperature greater than or equal to about 350 degrees Celsius. In another aspect of the third major aspect, none of the process steps occurs at a temperature greater than about 400 degrees Celsius. In another aspect of the third main aspect, no interfacial layer is deposited between the ferroelectric layer and the first electrode or between the ferroelectric layer and the second electrode. In another aspect of the third major aspect, the first gas or the second gas comprises ozone delivered at a volume fraction between about 2% and about 50%. In another aspect of the third main aspect, the method additionally comprises an ozone pulsing step prior to depositing the second electrode. In another aspect of the third major aspect, the ozone pulsing step delivers a gas stream comprising between about 2% and about 50% ozone by volume. In another aspect of the third principal aspect, the deposited crystalline material exhibits remanent magnetic polarization without additional heat treatment. In another aspect of the third major aspect, the deposited crystalline material has a residual magnetic polarization (Pr) greater than 8 μC/cm ² or a total loop opening greater than 16 μC/cm ² . In another _aspect of the third main aspect, the first electrode comprises TiN and the interfacial layer comprises _TiOxNy , where x and y are integers. In another aspect of the third main aspect, the first electrode comprises tungsten (W) and the intermediate layer comprises _WOx , where x is an integer. In another aspect of the third main aspect, the first electrode comprises ruthenium (Ru) and the intermediate layer comprises _RuOx , where x is an integer. In another aspect of the third main aspect, the first electrode comprises tungsten and the second electrode comprises titanium nitride. In another aspect of the third major aspect, the annealing step is performed at a temperature less than or equal to about 400 degrees Celsius.

In another aspect of the first, second or third main aspect, the film comprises _{HfxZr1 -xO2 or HfO2} doped with La, Y, Gd or Sr. In another aspect of the first, second or third main aspect, the interleaved memory array comprises a ferroelectric tunnel junction as in any one of claims 1 to 23 or consists of a ferroelectric tunnel junction as in any one of claims 24 to 23 The ferroelectric tunnel junction produced by the method of any one of 66, the ferroelectric tunnel junction comprising a memory unit cell (memory unit cell). In another aspect of the first, second or third main aspect, a neuromorphic computing chip comprising a ferroelectric tunneling junction according to any one of claims 1 to 23, Wherein the ferroelectric tunnel junction is a synaptic device. In another aspect of the first, second or third aspect, the ferroelectric tunnel junction has a critical dimension of about 300 nm or less.

In another aspect, the advanced metallocene precursor is one or more precursors disclosed and/or claimed in US Pat. No. 8,568,530, the contents of which are hereby incorporated by reference in their entirety.

This descriptive paragraph does not explicitly describe every specific instance and/or progressively novel aspect of this disclosed and claimed subject matter. Instead, this descriptive paragraph merely provides a preliminary discussion of various specific examples and corresponding points of novelty beyond conventional technology and the art. For additional details and/or possible perspectives on the disclosed and claimed subject matter and embodiments, the reader is referred to the disclosed embodiments and corresponding drawings discussed further below.

For clarity, the order of discussion of the different steps described herein is presented. In general, the steps disclosed herein can be performed in any suitable order. Furthermore, although each of the various features, techniques, configurations, etc. disclosed herein may be discussed at different places in the disclosure, it is intended that the various concepts can be implemented independently of each other or in combination with each other as appropriate. Accordingly, the disclosed and claimed subject matter can be embodied and viewed in many different ways.

definition

Unless otherwise specified, the following expressions used in this specification and claims shall have the following meanings for this specification.

In this case, use of the singular includes the plural and "a" and "the" mean "at least one" unless expressly stated otherwise. Furthermore, the use of the word "comprise" and other forms is not limiting. In addition, expressions such as "element" or "component" include elements or components comprising one unit as well as elements or components comprising more than one unit, unless explicitly stated otherwise. As used herein, unless stated otherwise, the conjunction "and" is intended to be inclusive and the conjunction "or" is not intended to be exclusive. For example, the phrase "or" is intended to be exclusive. As used herein, the word "and/or" means any combination of the aforementioned elements, including the use of a single element.

The word "about" when used in connection with a measurable numerical variable means the indicated value of the variable and all values of the variable within the experimental error of the indicated value (for example, within the 95% confidence limit of the mean) or within Within the percentage range of the indicated value (for example, ± 10%, ± 5%), whichever is greater.

For the purposes of this invention and its claim claims, the numbering scheme for the Periodic Table Groups is according to the IUPAC Periodic Table of the Elements.

The word "and/or" as used herein in the phrase "A and/or B" is intended to include "A and B", "A or B", "A" and "B".

The terms "substituent", "radical", "group" and "moiety" are used interchangeably.

As used herein, the terms "metal-containing complex" (or more simply, "complex") and "precursor" are used interchangeably and mean that they can be prepared by a deposition process such as, for example, ALD or CVD A metal-containing molecule or compound containing a metal film. The metal-containing complex can be deposited, adsorbed, decomposed, delivered and/or passed through the substrate or its surface to form a metal-containing film.

As used herein, the phrase "metal-containing film" includes not only elemental metal films as more fully defined below, but also films containing metal and one or more elements, for example, metal nitride films, metal silicide films, metal carbide films, film etc.

As used herein, the terms "elemental metal," "elemental metal film," and "pure metal film" are used interchangeably and mean a film consisting of, or consisting essentially of, a pure metal. For example, the elemental metal film can comprise 100% pure metal or the elemental metal film can comprise at least about 70%, at least about 80%, at least about 90%, at least about 95%, at least about 96%, at least about 97%, At least about 98%, at least about 99%, at least about 99.9%, or at least about 99.99% pure metal and one or more impurities. However, films comprising elemental metals differ from binary films comprising metals and nonmetals (e.g., C, N, O) and ternary films comprising metals and two nonmetals (e.g., C, N, O), however, Films containing elemental metals may include some amount of impurities. Unless the context indicates otherwise, the expression "metal film" should be interpreted to mean an elemental metal film.

As used herein, the terms "deposition process" and "thermal deposition" are used to denote any type of deposition technique, including but not limited to CVD and ALD. In various embodiments, CVD can take the form of conventional (ie, continuous flow) CVD, liquid injection CVD, plasma enhanced CVD, or light assisted CVD. CVD can also take the form of pulse technology, namely pulse CVD. ALD is used to form metal-containing films by vaporizing and/or passing at least one metal complex disclosed herein over a substrate surface. For conventional ALD processes see, for example, George SM et al., J. Phys. Chem., 1996, 100 , 13121-13131. In other embodiments, ALD may take the form of conventional (ie, pulse infusion) ALD, liquid infusion ALD, light assisted ALD, plasma assisted ALD, or plasma enhanced ALD. The phrase "vapor deposition process" additionally includes those described in Chemical Vapor Deposition: Precursors, Processes, and Applications ; Jones, AC; Hitchman, ML, Eds. The Royal Society of Chemistry: Cambridge, 2009; Chapter 1, pp 1–36 Various vapor deposition techniques.

Unless otherwise specified, "alkyl" means can be straight chain, branched (for example, methyl, ethyl, propyl, isopropyl, tert-butyl, etc.), cyclic (for example, cyclohexyl, cyclopropyl group, cyclopentyl, etc.) or polycyclic (eg, norbornyl, adamantyl, etc.). Suitable acyclic groups may be methyl, ethyl, n- or i-propyl, n-, i- or tert-butyl, linear or branched pentyl, hexyl, heptyl, octyl , Decyl, Dodecyl, Tetradecyl and Hexadecyl. Unless otherwise specified, alkyl means a moiety of 1 to 10 carbon atoms. The cyclic alkyl group may be monocyclic or polycyclic. Suitable examples of monocycloalkyl include substituted cyclopentyl, cyclohexyl and cycloheptyl. The substituent can be any acyclic alkyl group described herein. As described herein, the cyclic alkyl group may have any acyclic alkyl group as a substituent. These alkyl moieties can be substituted or unsubstituted.

"Haloalkyl" means a straight chain, cyclic or branched saturated alkyl group as defined above in which one or more hydrogens have been replaced by a halogen (eg, F, Cl, Br and I). Thus, by way of example, fluorinated alkyl (aka "fluoroalkyl") denotes a straight chain, cyclic or branched saturated alkyl group as defined above in which one or more hydrogens have been replaced by fluorine (e.g., trifluoro methyl, perfluoroethyl, 2,2,2-trifluoroethyl, perfluoroisopropyl, perfluorocyclohexyl, etc.). The haloalkyl moiety (eg, fluoroalkyl moiety), if not perhalogenated/polyhalogenated, may be unsubstituted or otherwise substituted.

The section headings used herein are for organizational purposes and should not be construed as limiting the subject matter described. All documents or portions of documents cited in this case, including but not limited to, patents, patent applications, articles, books, and treatises, are hereby incorporated by reference in their entirety for any purpose. To the extent any incorporated literature and similar sources define a term in a manner that contradicts the definition of that term in this case, this case controls.

It should be understood that both the foregoing general description and the following detailed description are illustrative and explanatory in nature and not restrictive of what is claimed. The purpose, features, advantages, and ideas of the disclosed subject matter will be apparent to those skilled in the art from the description provided in the specification, and those skilled in the art will be able to easily based on the description presented herein To practice the disclosure target. Any description of "preferred embodiments" and/or examples showing preferred modes for practicing the disclosed subject matter are included for purposes of explanation and are not intended to limit the scope of the claims.

It will also be apparent to those skilled in the art that various modifications can be made on how to practice the disclosed subject matter based on the aspects described in the specification without departing from the spirit and scope of the disclosed subject matter herein.

I. Ferroelectric Tunneling Junction with Multilevel Switching

Ferroelectric tunnel junctions (FTJs) have recently been investigated as one of the best candidates for memristors or artificial synapses, thanks to their unique analog programming basis for neuromorphic computing applications. ALD HZO film deposited at high temperature with specific precursors (HfD-04 and ZrD-04) sandwiched between TiN and W electrodes and application of specific post-metal annealing (PMA) allows multi-level programming up to 4 levels , and the retention is comparable to current state of the art generally using FTJs with double-layer stacks of higher complexity. This disclosure paves the way for future implementations of FTJs in neuromorphic computing chips.

This disclosure demonstrates a new technique for introducing asymmetry between the top and bottom electrodes. This can be achieved by high temperature (>300C) atomic layer deposition (ALD) of hafnium zirconium oxide (HZO) oxidized by alternating cycles of the Hf and Zr precursors (HfD-04 and ZrD-04) with an ozone pulse in between. contributed to.

This deposition builds the FTJ stack in such a way that it can be fabricated without any interfacial dielectric layer and can be switched between high memory regimes (2x to 10x). In state-of-the-art systems for fabricating ferroelectric memory devices, lower temperature ALD is typically used to deposit FE material, rendering the film as-deposited amorphous and thus non-FE, followed by high temperature annealing (>500C) to crystallize the film And activate the FE properties of the membrane. For FTJs with an interfacial layer, additional processing steps are required to deposit this interfacial material. Since the precursor can handle high temperature (>300C), the process integration and stacking can obtain the original deposited FE film. Furthermore, the process inherently oxidizes the bottom electrode (due to its high temperature and highly reactive ozone process) to produce interfacial metal oxides, thereby introducing the asymmetry required for the FTJ operation. Further annealing above this deposition temperature can be introduced to improve FE memory range and reliability metrics such as retention and endurance.

Furthermore, with the optimization of the HZO film, the FTJ stack exhibits good tunability of the tunneling resistance (TER), which makes it programmable up to 4 different stages, each with a good memory retention of at least 10 ³ s. The meaning of the 4 different memory levels allows storing up to 2 bits of data in a single FTJ cell, as opposed to storing 1 bit per cell in the binary switch FTJ. Moderate choice of ALD deposition temperature, ozone dilution, and post-metal annealing conditions are fundamental to obtain the desired orthorhombic phase required for ferroelectric multi-domain switches, which is crucial for multi-level switching in FTJs.

It has been demonstrated that in addition to storing multi-bit digital data, the FTJ unit cell can also be used as an analog memory that can store its resistance value that can be gradually adjusted within a certain range. This FTJ exhibits a hitherto unproven >2x dynamic range when gradually switching the resistance in the FTJ.

This disclosure shows for the first time a BEOL compatible process in which a hafnium zirconium oxide (HZO) switching layer is sandwiched between an asymmetric TiN electrode and a W electrode, with multi-level programming of up to 4 states and the states are passed through at least Good hold for 10 ³ seconds. During _HZO deposition, an oxidized interfacial layer ( _TiOxNy ) was created by oxidizing the TiN bottom electrode interface. The advantage of this step is that it occurs concomitantly in the deposition process and does not require additional process steps. In another embodiment, the first electrode comprises W and the oxidized interfacial layer comprises WO _x . In another specific example, the first electrode comprises Ru and the oxidized interfacial layer comprises _RuOx .

Intrinsically ferroelectric thin film materials and methods of using them that address the above problems are disclosed herein and in U.S. Provisional Patent Application No. 63/040,097 (Attorney Docket P20-094 US-PRO) filed June 17, 2020 and 2021 PCT Application No. PCT/EP2021/066028 (P20-094 WO-PCT) filed on 15 June. These applications are incorporated by reference in their entirety. In doing so, the materials and methods described herein reduce processing time, making them especially amenable to current process requirements. This disclosure relates to FTJs with 9 or more orders of different resistances. Those skilled in the art can readily appreciate the potential for subsequent optimization of interfaces, electrodes, and thermal treatment conditions after deposition of these materials.

II. Intrinsically Ferroelectric Materials

As noted above, the disclosed and claimed subject matter pertains to crystalline ferroelectric thin film materials comprising a mixture of hafnium oxide and zirconium oxide, the crystalline ferroelectric material comprising Electrophases; and methods for preparing and depositing these materials. In another aspect, the ferroelectric material has a majority volume fraction of the ferroelectric phase. Clearly, these materials exhibit ferroelectric properties without the need for further processing, such as subsequent coating steps or annealing steps. To be ferroelectric, a material is produced that has one or more of: (i) remanent polarization or (ii) a polarization field curve with hysteresis and loop opening.

In order to be ferroelectric, the material must have an arrangement of atoms capable of supporting ferroelectricity in certain parts of the film. Preferably, a substantial portion of the film volume has an arrangement of atoms that supports ferroelectricity. It is understood that for thin films, doped materials, and some laminated materials, the phase distribution in the material may not be readily determined by X-ray diffraction. In this case, any other suitable technique for establishing the phase of the film, such as Raman spectroscopy, infrared spectroscopy, X-ray absorption spectroscopy, transmission electron microscopy or a combination thereof, can be used to determine the phase distribution. For example, https://onlinelibrary.wiley.com/doi/full/10.1002/pssb.201900285 describes a technique for confirming the phase of a film to within about 10%.

The material may comprise any suitable molar ratio of hafnium oxide to zirconium oxide - preferably a ratio between 1:3 and 3:1. The thickness of the ferroelectric material is any thickness suitable for a particular application; the material can be made thicker to increase the remanent magnetic polarization or to reduce leakage current through the material thickness. The material can be made thinner for geometric constraints or to increase the capacitance of the film.

A preferred thickness range of the ferroelectric film is about 0.2 nm to about 20 nm, more preferably about 0.2 nm to 10 nm. It is also preferred that the material is formed into a film having a thickness of about 10 nm or less. In some embodiments, it is preferred that the material forms a film having a thickness of about 5 nm or less.

However, as noted above, the preferred and/or desired thickness will vary depending on the particular application. Thus, as previously stated, in certain embodiments, the material exhibits ferroelectric properties as thin films of about 20 nm or less. In another aspect, the material exhibits ferroelectric properties as thin films of about 15 nm or smaller. In another aspect, the material exhibits ferroelectric properties as thin films of about 10 nm or less. In another aspect, the material exhibits ferroelectric properties as thin films of about 5 nm or less. In another aspect, the material exhibits ferroelectric properties as thin films of about 3 nm or less. In another aspect, the material exhibits ferroelectric properties as thin films of about 1 nm or smaller. In another aspect, the material exhibits ferroelectric properties as thin films of about 0.5 nm or smaller. In another aspect, the material exhibits ferroelectric properties as thin films of about 0.2 nm or smaller. In another aspect, the material exhibits ferroelectric properties as a thin film between about 0.2 nm to about 20 nm. In another aspect, the material exhibits ferroelectric properties as a thin film between about 0.2 nm to about 15 nm. In another aspect, the material exhibits ferroelectric properties as a thin film between about 0.2 nm to about 10 nm. In another aspect, the material exhibits ferroelectric properties as a thin film between about 0.2 nm to about 5 nm. In another aspect, the material exhibits ferroelectric properties as a thin film between about 0.2 nm to about 3 nm. In another aspect, the material exhibits ferroelectric properties as a thin film of between about 0.2 nm to about 1 nm. nature. In another aspect, the material exhibits ferroelectric properties as a thin film of between about 0.2 nm to about 1 nm.

In the disclosed and claimed material, a substantial portion of about 40% or more of the crystalline material is in the ferroelectric phase, such that the total amount of non-ferroelectric atomic arrangement components is less than about 60% of the total volume of the material. In another embodiment, the total amount of non-ferroelectric atomic arrangement components is less than about 50% of the total volume of the material. In another embodiment, the total amount of non-ferroelectric atomic arrangement components is less than about 40% of the total volume of the material. In another embodiment, the total amount of non-ferroelectric atomic arrangement components is less than about 30% of the total volume of the material. In another embodiment, the total amount of non-ferroelectric atomic arrangement components is less than about 25% of the total volume of the material. In another embodiment, the total amount of non-ferroelectric atomic arrangement components is less than about 20% of the total volume of the material. In another embodiment, the total amount of non-ferroelectric atomic arrangement components is less than about 15% of the total volume of the material. In another embodiment, the total amount of non-ferroelectric atomic arrangement components is less than about 10% of the total volume of the material. In another embodiment, the total amount of non-ferroelectric atomic arrangement components is less than about 5% of the total volume of the material.

Furthermore, in the disclosed and claimed material, less than about 60% of the total volume of the material constitutes a non-ferroelectric monoclinic phase component. Thus, in one embodiment of the disclosed and claimed material, the monoclinic phase component is less than about 50% of the total volume of the material. In another specific example, the monoclinic phase component is less than about 40% of the total volume of the material. In another specific example, the monoclinic phase component is less than about 30% of the total volume of the material. In another specific example, the monoclinic phase component is less than about 25% of the total volume of the material. In another specific example, the monoclinic phase component is less than about 20% of the total volume of the material. In another specific example, the monoclinic phase component is less than about 15% of the total volume of the material. In another specific example, the monoclinic phase component is less than about 10% of the total volume of the material. In another specific example, the monoclinic phase component is less than about 5% of the total volume of the material.

In the disclosed and claimed subject matter, the preferred carbon content of the material is less than about 6 atomic percent as measured by a suitable technique, such as X-ray photoelectron spectroscopy. In another aspect, the carbon content is less than about 5 atomic percent. In another aspect, the carbon content is less than about 4 atomic percent. In another aspect, the carbon content is less than about 3 atomic percent. In another aspect, the carbon content is less than about 2 atomic percent. In another aspect, the carbon content is less than about 1 atomic percent. In another aspect, the carbon content is between about 1 atomic percent and about 6 percent. In another aspect, the carbon content is between about 1 atomic percent and about 5 percent. In another aspect, the carbon content is between about 1 atomic percent and about 4 atomic percent. In another aspect, the carbon content is between about 1 atomic percent and about 3 percent. In another aspect, the carbon content is between about 1 atomic percent and about 2 percent.

其中      M = Zr或Hf，並且 R ¹、R ²、R ³、R ⁴、R ⁵、R ⁶、R ⁷及R ⁸係各自獨立地選自C ₁-C ₆直鏈烷基、C ₁-C ₆支鏈烷基、C ₁-C ₆鹵代直鏈烷基及C ₁-C ₆鹵代支鏈烷基。 The intrinsic ferroelectric material is derived from a metallocene precursor selected from the group having the formula I (“(R ¹ -Cp)(R ² -Cp)-M-(OR ³ )(R ⁴ )” , wherein Cp is cyclopentadienyl) and/or formula II ("(R ⁵ -Cp)(R ⁶ -Cp)-M-(R ⁷ )(R ⁸ )", wherein Cp is cyclopentadienyl ) advanced metallocene precursors:

Where M = Zr or Hf, and R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently selected from C ₁ -C ₆ linear alkyl, C ₁ - C ₆ branched chain alkyl, C ₁ -C ₆ halogenated straight chain alkyl and C ₁ -C ₆ halogenated branched chain alkyl.

In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula I is preferably a C ₁ -C ₆ linear alkyl group. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula I is preferably the same C ₁ -C ₆ linear alkyl group. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula I is preferably methyl. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula I is preferably ethyl. In another aspect, each of R ¹ , R ² , R ⁵ and R ⁶ in Formula I is preferably ethyl. In another aspect, each of R ³ , R ⁴ , R ⁷ and R ⁸ in formula I is preferably methyl. In another aspect, each of R ¹ , R ² , R ⁵ and R ⁶ in Formula I is preferably ethyl and each of R ³ , R ⁴ , R ⁷ and R ⁸ is preferably methyl.

In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in formula II is preferably a C ₁ -C ₆ linear alkyl group. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula II is preferably the same C ₁ -C ₆ linear alkyl group. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula II is preferably methyl. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in formula II is preferably ethyl. In another aspect, each of R ¹ , R ² , R ⁵ and R ⁶ in formula II is preferably ethyl. In another aspect, each of R ³ , R ⁴ , R ⁷ and R ⁸ in formula II is preferably methyl. In another aspect, each of R ¹ , R ² , R ⁵ and R ⁶ in Formula II is preferably ethyl and each of R ³ , R ⁴ , R ⁷ and R ⁸ is preferably methyl.

In another aspect, the advanced metallocene precursor system (MeCp) ₂ Zr(OMe)Me, (MeCp) ₂ Hf(OMe)Me, (MeCp) ₂ Zr(Me) ₂ , (MeCp) ₂ Hf( _{one or _ _ _ _ _} many.

In another aspect, the advanced metallocene precursor system is a mixture of (MeCp) ₂ Zr(OMe)Me and (MeCp) ₂ Hf(OMe)Me, (MeCp) ₂ Hf(Me) ₂ and (MeCp) ₂ The mixture of Hf(Me) ₂ , the mixture of (EtCp) ₂ Zr(OMe)Me and (EtCp) ₂ Hf(OMe)Me and the mixture of (EtCp) ₂ Hf(Me) ₂ and (EtCp) ₂ Hf(Me) ₂ One or more of a mixture.

In another aspect, the advanced metallocene precursor is one or more of the precursors disclosed and/or claimed in U.S. Patent No. 8,568,530, the contents of which are hereby incorporated by reference in their entirety. .

III. Methods of Fabricating and Depositing Intrinsically Ferroelectric Materials

As indicated above, in another aspect the disclosed and claimed subject matter relates to the methods of making and depositing the intrinsic ferroelectric materials disclosed herein. In this method, the disclosed and claimed intrinsically ferroelectric materials are prepared by iterative deposition and purging of (i) metallocene precursors and (ii) reactants.

A. Metallocene Precursors

其中      M = Zr或Hf，並且 R ¹、R ²、R ³、R ⁴、R ⁵、R ⁶、R ⁷及R ⁸係各自獨立地選自C ₁-C ₆直鏈烷基、C ₁-C ₆支鏈烷基、C ₁-C ₆鹵代直鏈烷基及C ₁-C ₆鹵代支鏈烷基。 As shown above, the ferroelectric material is derived from an advanced metallocene precursor having the formula I (“(R ¹ -Cp)(R ² -Cp)-M-(OR ³ )(R ⁴ )", wherein Cp is cyclopentadienyl) and/or formula II ("(R ⁵ -Cp)(R ⁶ -Cp)-M-(R ⁷ )(R ⁸ )", wherein Cp is cyclopentadienyl alkenyl):

Where M = Zr or Hf, and R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently selected from C ₁ -C ₆ linear alkyl, C ₁ - C ₆ branched chain alkyl, C ₁ -C ₆ halogenated straight chain alkyl and C ₁ -C ₆ halogenated branched chain alkyl.

In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula I is preferably a C ₁ -C ₆ linear alkyl group. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula I is preferably the same C ₁ -C ₆ linear alkyl group. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula I is preferably methyl. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula I is preferably ethyl. In another aspect, each of R ¹ , R ² , R ⁵ and R ⁶ in Formula I is preferably ethyl. In another aspect, each of R ³ , R ⁴ , R ⁷ and R ⁸ in formula I is preferably methyl. In another aspect, each of R ¹ , R ² , R ⁵ and R ⁶ in Formula I is preferably ethyl and each of R ³ , R ⁴ , R ⁷ and R ⁸ is preferably methyl.

In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in formula II is preferably a C ₁ -C ₆ linear alkyl group. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula II is preferably the same C ₁ -C ₆ linear alkyl group. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula II is preferably methyl. In another aspect, each of R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ in Formula II is preferably ethyl. In another aspect, each of R ¹ , R ² , R ⁵ and R ⁶ in formula II is preferably ethyl. In another aspect, each of R ³ , R ⁴ , R ⁷ and R ⁸ in formula II is preferably methyl. In another aspect, each of R ¹ , R ² , R ⁵ and R ⁶ in Formula II is preferably ethyl and each of R ³ , R ⁴ , R ⁷ and R ⁸ is preferably methyl.

In another aspect, the advanced metallocene precursor system (MeCp) ₂ Zr(OMe)Me, (MeCp) ₂ Hf(OMe)Me, (MeCp) ₂ Zr(Me) ₂ , (MeCp) ₂ Hf( _{one or _ _ _ _ _} many.

In another aspect, the advanced metallocene precursor system is a mixture of (MeCp) ₂ Zr(OMe)Me and (MeCp) ₂ Hf(OMe)Me, (MeCp) ₂ Hf(Me) ₂ and (MeCp) ₂ The mixture of Hf(Me) ₂ , the mixture of (EtCp) ₂ Zr(OMe)Me and (EtCp) ₂ Hf(OMe)Me and the mixture of (EtCp) ₂ Hf(Me) ₂ and (EtCp) ₂ Hf(Me) ₂ One or more of a mixture.

In another aspect, the advanced metallocene precursor is one or more of the precursors disclosed and/or claimed in U.S. Patent No. 8,568,530, the contents of which are hereby incorporated by reference in their entirety. .

Generally, precursors suitable for making the intrinsic ferroelectric material can be deposited at or near the crystallization temperature of the desired ferroelectric material, typically between about 200°C and about 570°C, depending on the composition of the material , substrate and reactor design and other factors. A preferred temperature is about 300°C (or generally between about 280°C and about 300°C), and the preferred temperature range is below about 450°C, more preferably below about 340°C. However, those skilled in the art will recognize that other temperatures may depend on the particular precursor used, and such precursors are also within the scope of the disclosed and claimed subject matter. It should also be noted that decomposition of precursors other than those listed here can occur within the stated temperature range. Decomposition products, especially carbon and organic matter, may be incorporated into the deposited hafnium oxide or zirconium oxide material. Although the incorporation of this carbon may contribute to the stabilization of the ferroelectric phase, this may be undesirable due to material purity. Thus, as discussed above, the preferred carbon content of the material is less than about 6 atomic percent.

B. Reactants

The reactant is a reactive gas containing one or more of oxygen (eg, ozone, elemental oxygen, molecular oxygen/O ₂ ), water, hydrogen peroxide, and nitrous oxide. In one embodiment, ozone is a preferred reactive gas. In another embodiment, water is a preferred reactant gas.

2A-2D illustrate alternative embodiments of the ferroelectric tunnel junctions disclosed herein. FIG. 2A shows an FTJ with a top electrode 102 , a layer of ferroelectric material 104 and a bottom electrode 106 on a substrate 108 . 2B shows an FTJ embodiment 200a having a top electrode 202a, a top interface layer 210a, a layer of ferroelectric material 204a, a bottom interface layer 220a, and a bottom electrode 206a on a substrate (not shown). Figure 2C shows an FTJ embodiment 200b having a top electrode 202b, a layer of ferroelectric material 204b, a bottom interface layer 220b, and a bottom electrode 206b on a substrate (not shown). Figure 2D shows an FTJ embodiment 200c having a top electrode 202c, a top interface layer 210c, a layer of ferroelectric material 204c, and a bottom electrode 206c on a substrate (not shown). In the specific example illustrated in FIG. 5A, the top electrode comprises TiN, the ferroelectric material layer comprises hafnium oxide and zirconium oxide (HZO), the bottom interface layer comprises tungsten oxide (WOx), and the bottom layer comprises tungsten.

C. Process steps

Figure 3A illustrates a specific example of the equations for making and depositing the intrinsic ferroelectric materials described herein. As illustrated, the substrate 502 is subjected to an ALD cycle 504 in which the substrate 502 is exposed to the vapor 201 to form and deposit the intrinsic ferroelectric material as a thin film layer 300 . Layer 300 is formed without further heat treatment or face protection and exhibits intrinsic ferroelectric properties (ie, as-deposited). Of course, those skilled in the art recognize that layer 300 may thereafter be annealed and/or protected as desired, but doing so is not necessary to observe the ferroelectric behavior of the as-deposited layer. For example, energy can be thereafter delivered by, but not limited to, heat, plasma, pulsed plasma, helical plasma, high-density plasma, inductively coupled plasma, X-rays, electron beams, photons, remote plasma Methods and combinations thereof are applied to the material.

The composition of the vapor 301 changes during the ALD cycle 504 . In particular, substrate 502 is alternately exposed to metallocene precursor 505 followed by a purge, then exposed to reactant 506 followed by another purge. The process continues until the desired thickness of layer 300 is obtained. Although ALD is the preferred vapor deposition technique, any suitable vapor deposition technique may be used, such as CVD or pulsed CVD. Thus, for example, in FIG. 3A , ALD cycle 504 may be replaced by a CVD process in which metallocene precursor 505 and reactant 506 are provided as a mixture in vapor 201 and simultaneously to substrate 502 .

The appropriate molar ratio of hafnium oxide to zirconium oxide can be produced by several methods, including introducing a hafnium-containing precursor during some of these cycles, and a zirconium-containing precursor during other cycles. The cycles can be alternated, combined, or arranged in any other suitable order to produce the overall desired molar ratio, as both intimately mixed materials and nanolaminates exhibit desirable ferroelectric properties. It should be noted that other elements can be added to the hafnium oxide-zirconia material by adding appropriate precursors together with the hafnium and zirconium precursors, or in separate cycles.

The substrate 502 on which the intrinsic ferroelectric material is formed as layer 300 may comprise any suitable material, including semiconductor materials such as silicon, germanium, III-V materials, transition metal dichalcogenides and mixtures thereof, metals, and Conductive ceramics such as titanium nitride, titanium, tantalum, tantalum nitride, tungsten, platinum, rhodium, molybdenum, cobalt, ruthenium, palladium or their mixtures; or dielectrics such as silicon oxide, silicon nitride, aluminum oxide, titanium oxide , Other ferroelectric materials including hafnium oxide and zirconium oxide compositions, magnetic materials and mixtures or stacks thereof.

Substrate 302 may be suitably patterned or textured with any suitable topography, including planar surfaces, grooves, vias, or nanostructured surfaces, as desired. This list represents typical substrates that can be used in ferroelectric applications, but should not be considered limiting, as many other suitable compositions and surface patterns will be apparent to those skilled in the art. In this regard, the substrate is known to have certain effects on the atomic arrangement and phase of the film formed thereon, including affecting the crystallographic orientation and crystallization temperature of the film. Regardless of the particular substrate and the extent of this effect, the intrinsic ferroelectric materials described herein and deposited on such substrates still have a substantial portion of their volume in the as-deposited ferroelectric phase.

Figure 3A illustrates another embodiment of a process for fabricating and depositing the intrinsic ferroelectric materials described herein. In this particular example, an intrinsic ferroelectric material of mixed hafnium oxide and zirconium oxide was prepared as a layer 501 with a thickness of about 8.4 nm and deposited on PVD TiN (which was in direct contact with the ferroelectric material), thermally grown _SiO2 layers and silicon wafers on the stacked substrate 302 . The 501 layer was formed without further heat treatment or face protection. In this specific example, the molar ratio of hafnium oxide to zirconium oxide is about 1:1, and the error range is about 10%. The ferroelectric material is obtained by alternating the first cycle 303 (which includes the steps of (i) pulse (MeCp) ₂ Zr(OMe)Me 304, (ii) purge, (iii) pulse ozone 305 and (iv) purge) and In the second cycle 306 (which includes the steps of (i) pulse (MeCp) ₂ Hf(OMe)Me 307, (ii) purge, (iii) pulse ozone 308 and (iv) purge), the ferroelectric Materials are prepared from this vapor and deposited as layer 501 .

Those _skilled in the art will recognize that other precursors such as (MeCp) _2HfMe2 and (MeCp) _2ZrMe2 and other reactants such as water, hydrogen peroxide or _oxygen plasma can also or alternatively be used . Those skilled in the art will further recognize that the pulse and purge times, respectively, can vary from device to device. In a specific example, the pulse lasts from about 2 to about 3 seconds, followed by a purge of about 10 seconds. In another specific example, the pulse lasts from about 10 seconds to about 15 seconds, followed by a purge of about 30 seconds to about 60 seconds. In another embodiment, the order of deposition of the precursors may be reversed.

Figure 3B illustrates a specific example of a layer ₅₀₁ comprising intrinsic ferroelectric _ZrO2HfO2 on a stack 502 comprising a bottom electrode (TiN), thermal _SiO2 and p-type Si.

3C illustrates providing a substrate 3002, providing a bottom electrode 3004, exposing the bottom electrode to Hf and/or Zr precursors 3006, exposing the bottom electrode to a reactive gas 3008, repeating 3009 steps 3006 and 3008 to achieve the desired thickness 3010, providing the top electrode 3012, and performing the process of the annealing step 3014. In a preferred embodiment, all steps 3002 to 3014 are performed at a temperature below 400 degrees Celsius.

FIG. 4A illustrates a schematic diagram of a metal-ferroelectric-metal (MFM) capacitor used to measure properties of HZO thin films. Figure 4B illustrates a schematic diagram of a submicron scale FTJ device on an internal test mount. To confirm the ferroelectric switching of this HZO thin film, a large-area metal-ferroelectric-metal (MFM) capacitor was fabricated (Fig. 4A). Then, to integrate this HZO thin film in the FTJ stack and confirm efficient and reliable memory switching, sub-micron scale FTJs were formed on internal test mounts with different embedded polysilicon series resistors. Figure 4B shows a schematic diagram of the FTJ device after integration. In this assignment, a 20 kΩ series resistor was used during the electrical characterization of the FTJ device to avoid the chance that this dielectric breakdown could occur. Note that the same device stack is used in both the MFM capacitor and the FTJ device to maintain consistency between different devices.

For simple large (~200 μm diameter) MFM stack fabrication, initially we deposited a thick W layer (50 nm) as the bottom electrode (BE) using a PVD process. Then, the HZO film (about 4.5 nm) was deposited by ALD. Following the top electrode (TE) deposition (50 nm TiN deposited by PVD), PMA, patterning of the TE and SF6/Ar etch were performed in _N2 at 400 °C for 2 min. These simple large MFM stacks are used to measure the FE polarization characteristics of this film, since measuring polarization requires measuring the displacement current, which is close to the instrument background for most common high-k dielectrics Instrument noise floor, which is not the same for smaller area (<1 μm ² ) devices. On the other hand, the leakage current of large devices is high enough to meet the requirements of sensitive measurements. In order to integrate the sub-micron FTJ device, the HZO FE film was selected to increase the current density to perform pulsed write and read operations at low voltage. Films were deposited on internal test mounts with 300 nm diameter tungsten plugs buried in _SiO2 . The process starts with ALD HZO deposition (about 4.5 nm), followed by 50 nm TiN TE deposition by PVD, 2 min PMA at 400°C in N ₂ , patterning of TE and finally SF ₆ /Ar Etching to define the TE region is similar to the MFM process flow.

Figure 5C illustrates the grazing incidence XRD pattern of this intrinsic ferroelectric material (thin HZO after 2 min PMA in _N2 at 400C). Both W and WO ₃ peaks are visible. The inset portion of this Figure 5C shows the presence of a highly non-monoclinic phase of HZO and the absence of a monoclinic peak. As shown in FIG. 5C , the crystallization peaks of the material constituting layer 501 show a low monoclinic composition and a high non-monoclinic composition. By fitting the peak with the technique described by McBriarty et al., https://onlinelibrary.wiley.com/doi/full/10.1002/pssb.201900285, and using the peak area, the volume of the material making up layer 501 was calculated. The oblique crystal fraction is less than 25%, which is the preferred maximum volume fraction of monoclinic and non-ferroelectric materials. We can observe a very sharp metallic W peak from this BE. However, in addition to this metallic W peak, we also observed a prominent peak of WO _x , which confirmed the findings of the EELS spectra. Careful inspection (Inset 5C) of this HZO peak reveals mostly non-monoclinic grains, indirectly suggesting an orthorhombic (ferroelectric) or tetragonal (antiferroelectric) phase. No small peak associated with a small amount of thermodynamically stable monoclinic phase was detected. These XRD results indirectly suggest that ALD HZO film growth using advanced metallocene-type precursors allows for a BEOL-compatible process suitable for different non-volatile memory and neuromorphic computing applications.

In some embodiments, the FTJs can be incorporated into interleaved arrays or memory unit cells. In some embodiments, the FTJ can be incorporated into a neuromorphic computing chip or a synaptic device such as a synaptic memristor or a synaptic transistor.

A specific example of a process using ALD to fabricate and deposit the intrinsic ferroelectric materials described herein. The method includes several steps that can be extended with additional and/or optional steps. Step 1 involves providing the substrate at a deposition temperature between about 265°C and about 500°C, but preferably at or around 300°C (e.g., above about 285°C and At or below about 300°C) and below 340°C. Step 2 comprises (i) exposing the substrate to a first precursor containing hafnium or zirconium or both hafnium and zirconium that does not decompose at the deposition temperature, and (ii) purging. Step 3 includes (i) exposing the substrate to an oxygen-containing reactive gas, and (ii) purging. Step 4 includes (i) exposing the substrate to a second precursor containing zirconium or hafnium or both hafnium and zirconium that does not decompose at the deposition temperature, and (ii) purging. Step 5 includes exposing the substrate to an oxygen-containing reactive gas. Optional step 6 includes repeating steps 2 to 5 until a hafnium oxide and zirconium oxide film of desired thickness with a molar ratio between about 1:3 and about 3:1 is formed.

In the processes of the present disclosure, the intrinsic ferroelectric material is formed and deposited in an as-deposited state (i.e., without further annealing and/or masking) and is known by phase determination techniques or by those skilled in the art. Electrical testing (eg, XRD, XAS, TEM, polarization voltage testing, piezoelectric microscopy, or a combination thereof) of the film measures a substantial volume fraction of the ferroelectric phase. Metallocene precursors used and/or usable in the process of FIG. 6 include all of those disclosed and discussed above, including (MeCp) ₂ Zr(OMe)Me, (MeCp) 2 Hf(OMe)Me, (MeCp) ₂ Zr(OMe)Me, ( MeCp) ₂ Zr(Me) ₂ and (MeCp) ₂ Hf(Me) ₂ . The oxygen-containing reaction gas in step 3 and/or step 5 is preferably ozone. Those skilled in the art will recognize that other reactive gases may be used, including those specifically described above (eg, water, hydrogen peroxide). Example

Reference will now be made to a more specific embodiment of the present disclosure and to experimental results in support of this embodiment. The examples provided below are to more fully illustrate the disclosed subject matter and should not be construed as limiting the disclosed subject matter in any way. HZO film growth

The FE HZO film was grown at 355°C by atomic layer deposition involving a HZO supercycle with the exposure sequence of HfD-04 (bis(methylcyclopentadienyl)methoxymethyl-hafnium) /Ozone/ZrD-04 (Bis(methylcyclopentadienyl)methyl-zirconium methoxide)/Ozone. Both Hf-D04 and Zr-D04 are proprietary chemicals of EMD Electronics. Figure 1 shows that this dicyclopentadienyl precursor has an ALD interval at a higher temperature (300°C to 400°C) than the amide-type precursor, which allows the use of a lower temperature PMA process to Obtain desired HZO grains. We have deposited this film for two different ozone concentrations (4% and 20%), which were found to result in different ferroelectric properties. The HfD-04 and ZrD-04 precursors were maintained at ampoule temperatures of 125°C and 70°C, respectively, during deposition. Different ozone concentrations produced slightly different growth rates (4% ozone had slightly less growth per cycle). Device manufacturing

For simple metal-FE-metal (MFM) stack fabrication, we deposited W (50nm) as the bottom electrode (BE) using a PVD process. Then, the HZO film was deposited by ALD at a temperature of 325 degrees Celsius. This was followed by patterning of the top electrode (TE) (20 nm TiN or W deposited by PVD), PMA from 400 to 600 C for 2 min in _N2 ambient, followed by TE and _SF6 etch.

For this scaled device, films were deposited on prefabricated test mounts with 300 nm diameter tungsten plugs buried in _SiO2 (FIG. 6B). The process starts with ALD HZO deposition, followed by TE deposition (50 nm TiN) by PVD, 2 min PMA at 400°C in _N2 environment, photolithography to define TE areas and final _SF6 etch. Analysis of Physical Properties of HZO Films in Large Area FTJ Devices

5A-5B illustrate specific examples of HZO FTJ stacks of the present disclosure. Figure 5A is a cross-sectional TEM image of W(50nm)/HZO(4.5nm)/TiN(50nm) annealed in _N2 at 400 °C for 2 minutes. Figure 5B is an EELS drawing across the cross-section. The bottom interfacial layer (IL) shows the formation of WO _x .

The bottom (first) electrode and the top (second) electrode may be metal or semiconductor electrodes of a thickness ensuring good conduction. In the illustrated embodiment, the top electrode comprises titanium nitride. In other embodiments, the top electrode may comprise any one of titanium nitride, tungsten, nickel, ruthenium, platinum, and aluminum. In the illustrated specific example, 50 nm thick TiN was used.

In the illustrated embodiment, the bottom electrode comprises tungsten. In other embodiments, the top electrode may comprise any one of titanium nitride, tungsten, ruthenium, platinum, and aluminum. In this illustrated embodiment, a 50 nm thick W is used.

The interfacial layer is created during, before or after the HZO deposition. Oxidation of the W bottom electrode produces an interfacial layer comprising _WOx . In one embodiment, the interfacial layer comprises WO ₃ and the oxygen plasma pulsing step occurs prior to deposition of the ferroelectric material. The oxygen plasma pulsing step includes elemental oxygen (O), molecular oxygen ( _O2 ) and ozone ( _O3 ).

This EELS also shows that the ratio between Hf and Zr is close to 1:1. In order to confirm the crystallinity of this HZO film, XRD analysis was performed on the same sample. Figure 5C shows the XRD pattern of the HZO thin film. We can observe a very sharp metallic W peak from this BE. However, in addition to this metallic W peak, we also observed the main peak of WOx, which confirmed the findings of this EELS spectrum. Closer inspection (Inset 5C) of the HZO peak reveals mostly non-monoclinic grains, indirectly suggesting an orthorhombic (ferroelectric) or tetragonal (antiferroelectric) phase. No small peak associated with a small amount of thermodynamically stable monoclinic phase was found.

The ferroelectric layer contains Hf _x Zr _1-x O ₂ . In alternative embodiments, the ferroelectric layer may comprise _HfO2 doped with La, Y, Gd, Sr or combinations thereof.

In the illustrated embodiment, a post metal anneal (PMA) is performed at 400 degrees Celsius for 2 minutes.

6A illustrates a polarization-electric field diagram of an intrinsic ferroelectric material formed and deposited in the process illustrated in FIG. 4A, as measured using a ferroelectric tester. In order to characterize the fundamental ferroelectric properties of this material, we performed polarization pair electric field (PE) measurements using a typical double bipolar triangular pulse sequence at a frequency of 10 KHz. Figure 5 shows the PE characteristics of the new device and after wake-up stress (±1.5V, 1ms pulse width, 103 cycles). The new device shows a 2Pr interval close to 30 µC/cm ² . After a mild wake-up process, the 2Pr range was improved to 40 µC/cm ² . These results confirm that the BEOL-compatible integration of ferroelectric thin HZO (<5 nm) can be achieved using advanced metallocene precursors (HfD-04/ZrD-04) without the need for amide-based precursors such as TEMA-Hf/ZrD-04. PMA at higher temperatures (>= 500 °C) required for TEMA-Zr.

Note that the P-E loop is not symmetrical on the x-axis. This is due to the asymmetric nature of the stack created by the in situ growth of the interfaces WOx and dissimilar metals (W and TiN) at the bottom and top interfaces, respectively.

Figure 6B illustrates current-voltage DC sweeps of the scaled device before and after wake-up stress. Figure 6 shows the current-voltage (I-V) characteristics of the scaled FTJ device (300 nm tungsten plug diameter size) shown in Figure 4B. The device initially showed very small memory bins for DC sweeps up to 3V. However, after a wake-up cycle (±4.2V, 1μs pulse width (PW) for 103 cycles), this memory region opens significantly up to 10 times in the low electric field region below 1V. This switching operation is repeatable and does not include any sudden changes in current typically seen in resistive wire RRAM switches. This indirectly indicates that the current hysteresis is due to the polarization switching of the ferroelectric material.

Figure 7A illustrates the resistance of the scaling device versus programming voltage and shows the RV characteristics of an FTJ device over 20 cycles for a program pulse at a variable programming voltage (V _prog ) and at a fixed For a read pulse (read pulse) at a read voltage V _read =1.5V, the PW is maintained for 100 μs. From the RV signature (FIG. 7A), we observed that the low-resistance state (LRS) and high-resistance state (HRS) distribution remained tightly distributed over 20 cycles, with about 3 times the memory interval (cycle period of HRS and LRS The variability (σ _R /R) was 6.6% and 5.9%, respectively). Furthermore, the resistance range can be adjusted by changing the writing pulse width, as shown in FIG. 7( b ). Figure 7B illustrates the resistance of the scaling device versus programming voltage for different write pulse widths. These results indirectly suggest that this resistance interval can be tuned from about 1.3 times that of a 1 μs pulse to about 5 times that of a 1000 μs pulse. The dependence of this RV interval on pulse width is due to the depolarizing field due to incomplete polarizing charge screening at the contact. This is in contrast to wire-type breakdown in RRAM, where the HRS energy level is dominated by the tunneling barrier formed after the wire breaks and is thus less dependent on the pulse width. We also observed that the resistive switching was rather slow as the voltage amplitude varied. This indirectly suggests localized FE-domain switching that can be independently tuned by pulse width and pulse amplitude. Figure 7C shows the RV characteristics of 4 different devices. The graph represents low device-to-device variation and shows uniformity of film properties across the sample. Using different pulse amplitudes, we demonstrate progressive resistive switching between 4 stable energy levels of 4 different devices (Fig. 7D). A tight distribution of all 4 states was observed, confirming the uniformity of the film and the repeatability of the process.

The analog switching behavior required for in-memory computing architectures was demonstrated by switching the FTJ with a pulse train in which the resistance/conductivity was varied gradually over a factor of more than 2. To maintain high linearity, we chose a pulse sequence with increased pulse amplitude, keeping the pulse width constant. Figure 8A shows 15 pulse trains for increasing amplitudes (-2V to -4V for potentiation in -50 mV steps, +2.2V to +4.2V for depression in 50mV steps, and + 1.5V for a read voltage of 100μs PW) cycle ramp-up and ramp-down curves (conductivity during set and reset pulses vs. pulse number). In order to calculate the linearity and repeatability of the analog switch, the boost and decay curves of 15 cycles of the input pulse train were superimposed on each other with the intermediate response shown (FIG. 8B). We fit the median curve with the model reported in Figure 8C and extracted the nonlinearity (NL) metric measurements. We report NL values of 0.62 for attenuation and 2.0 for augmentation, which are among the best values reported by FTJ compared to recent works published in the literature. Similarly, we have tested this device for pulse sequences with constant pulse amplitude and width (Figures 8D to 8F). Figure 8E shows the superimposed response resulting from Figure 8D, and Figure 8F shows the extraction of NL metric measurements. In the case of the constant pulse test we used -3.3 V/100 µs for boost and +3.6 V/100 µs for cut. Constant pulse amplitude results in higher nonlinearity, which may not be suitable for in-memory computing applications. Nevertheless, it can still be switched in the form of multi-level digital memory which enables increased bit/cell memory density.

Figures 8A to 8F illustrate conductivity as a function of pulse number, illustrating the good linearity of the scale device for 4% ozone. Figure 9 illustrates the resistance versus voltage relationship after different post-metal annealing conditions. Figures 10A-10B illustrate multi-stage state retention forces measured at room temperature as a function of time.

Figure 9 shows the effect of annealing conditions on this RV interval. In this graph, the write PW of both devices is held at 100 μs. Only the duration of the anneal was varied, keeping the anneal temperature constant at 400°C. Furthermore, Figure 9 shows that a longer anneal of 30 minutes increases the memory interval from 3-fold to 5-fold, which means that a longer anneal time produces larger orthorhombic phase crystallites. To verify the reliability of our FTJ device, we also demonstrated the multi-stage retention and durability. In Figures 10A to 10B we show a multi-step retention measured at room temperature for 10 ³ s. Note that for programming the 4 different resistance states, we use the same conditions as in Figure 7D. LRS reveals a slight relaxation of this FE domain, indirectly suggesting that the different states may overlap after a longer time, but a stable 2-order retention for up to 10 years. Figure 11 shows the 10 ³ cycle endurance of read pulse execution with single-pulse programming technique and post-programming on our sub-micron device (programmed LRS state with -3.6V 100μs PW, programmed HRS state with 3.9V 100μs PW, and read different states with 1.5V 100μs PW). The second stylized state can get stable about 2 times the memory range with low variability. Retention loss and limited durability over time are two of the biggest challenges observed in the literature on FTJ devices, and optimizing the stack through interface engineering is critical to the adoption of this technology to enable neuromorphic hardware using memristors. important.

A major advantage of the present disclosure is the multi-level cell demonstration without resistance drift of the FTJ. Figures 10A and 10B show 4-stage resistive switching, where each resistive stage remains stable for 10Λ3 seconds. In FTJs, due to the relaxation of the electric dipole, the resistance interval collapses rapidly, making it difficult to exhibit multiple states. Moreover, multilevel switching depends on the existence of multiple domains and their local switching.

The advantage of this FTJ system is the simplified process flow. The exemplary FTJ stack can be fabricated without depositing any interfacial dielectric layer, thereby eliminating one process step from the process flow.

In this embodiment, the interfacial layer is created during HZO deposition. Oxidation of the TiN electrode produces _an interfacial layer comprising _TiOxNy . An oxygen plasma pulsing step occurs prior to the deposition of the ferroelectric material. The oxygen plasma pulsing step includes elemental oxygen (O), molecular oxygen ( _O2 ) and ozone ( _O3 ).

Another advantage of the present FTJ system is the lower overall thermal budget. It is very important to fabricate on-wafer back-end-of-line (BEOL) compliant memory at temperatures below 400C in any of its process steps. Typical HZO films are deposited in an amorphous state due to low-temperature ALD processes, so the FE domains require high-temperature annealing to be activated. The exemplary process utilizes high temperature ALD precursors to impart high as-deposited ferroelectricity to the film. Typically, the preferred deposition temperature is between 300°C and 350°C, followed by annealing at 400°C is sufficient to make it highly stable. This makes the process flow BEOL compatible.

Another advantage of the present FTJ system is faster read/write operations. Because the FTJ relies on tunneling resistance, the device has high resistance in both its low and high resistance states compared to other non-volatile memory technologies such as ReRAM and PCM. While this is desirable from an energy dissipation standpoint, too high a resistance requires high voltages to read, causing reliability issues, and slower pulses result in slower and more read and write speeds. prone to noise. Since we don't need any dielectric layers to create the asymmetry, and the film has high remanent polarization, the stack can be designed to be thin and still have enough FE dipoles to create memory compartments. This makes the exemplary FTJ stack highly scalable both in terms of the thickness of the ferroelectric material and the device area.

The table below illustrates the FTJ reference parameters for calibration devices from NamLab, IBM and Kioxia. The thermal budget is 400 degrees Celsius; the FE film thickness is 4.5 nm, the area is 0.09 µm ² , the on/off ratio is about 5.0, the nonlinearity is +0.62/-2.29, the RON is 100 Mohms, and the reading voltage The current density of LRS is 1.5 V, the LRS current density is 1.66x10 ^-3 A/cm ² , and the multi-step holding force is 4 steps (10 ³ seconds at 25 degrees Celsius).

This application demonstrates a scaled FTJ fabricated with BEOL compatible HZO process conditions that achieve analog resistance values with highly reliable device operation. This high-performance device can be achieved by a high-temperature ALD process using cyclopentadienyl precursors.

It will be apparent to those skilled in the art that various modifications and changes can be made to the disclosed subject matter and the specific embodiments provided herein without departing from the spirit or scope of the disclosed subject matter. Accordingly, it is intended that the disclosed subject matter, including the description provided by the following examples, cover modifications and variations of the disclosed subject matter that fall within the scope of any claims and their equivalents.

Materials and methods:

The metallocene precursor may be prepared according to US Patent No. 8,568,530 or otherwise prepared, the entirety of which is hereby incorporated herein. surface KPIs current works NamLab Al ₂ O ₃ /HZO IBM WO _x /HZO Kioxia SiO ₂ /HfSiO Thermal budget [°C] 400 600 375 1000 FE film thickness [nm] 4.5 12 4.9 4.5 Device area [µm ² ] 0.09 31415 14400 0.09 Switch ratio ~5 ~10 ~7 ~2.5 Nonlinearity* +2.0/-0.62 +0.85/-4.76 +1.9/-4.0 +2.2/-4.88 R _ON [MΩ] 100 1000 100 150 Read voltage [V] 1.5 2 0.3 3 Switching speed [µs] 100 10-100 50 2 LRS reading current density [A/cm ² ] 1.66×10 ^-3 6.3× ^10-10 8.3× ^10-10 2.2×10 ^-3 multi-stage retention 4th stage (at room temperature > 10 ³ seconds) 4th stage (about 10 ³ seconds at room temperature) 3rd stage (about 10 ⁵ seconds at room temperature) no report

While the present invention has been described and illustrated with a certain degree of particularity, it should be understood that this disclosure is done by way of example only, and that those skilled in the art can make further modifications without departing from the spirit and scope of the invention. Various changes are made to the conditions and sequence of steps.

100, 200a, 200b, 200c: ferromagnetic tunneling junctions 102, 202a, 202b, 202c: top electrodes 104, 204a, 204b, 204c, 300, 501: ferroelectric material layers 106, 206a, 206b, 206c: bottom electrodes 108, 302, 502: substrate 210a, 210c: top interface layer 220a, 220b: bottom interface layer 301: vapor 303: first cycle 304: (MeCp) _2Zr (OMe)Me 305, 308: ozone 306: second cycle 307: (MeCp) _2Hf (OMe)Me 504: ALD Cycle 505: Metallocene Precursors 506: Reactants

The accompanying drawings, which are incorporated to provide a further understanding of the disclosed subject matter and are incorporated in and constitute a part of this specification, illustrate specific examples of the disclosed subject matter and together with the description, serve to explain the principle of the disclosed subject matter. In this graph:

Figure 1 illustrates the ALD interval of different precursors for hafnium oxide and zirconium oxide deposition;

2A-2D illustrate alternative embodiments of ferroelectric tunneling junctions disclosed herein;

Figure 3A illustrates a specific example of a process for depositing examples of intrinsic ferroelectric materials disclosed herein on a substrate;

Figure 3B illustrates a specific example of a layer comprising an intrinsic ferroelectric material on a bottom electrode (TiN) on a substrate;

Figure 3C illustrates another process for depositing intrinsic ferroelectric material on the stack;

Figure 4A illustrates the schematic diagram of the metal-ferroelectric-metal (MFM) capacitor used to measure the properties of HZO thin films;

Figure 4B illustrates a schematic diagram of a submicron scale FTJ device on an in-house test vehicle;

Figure 5A illustrates a cross-sectional HR-TEM image of a HZO film deposited on a 50 nm tungsten electrode and covered with a 50 nm TiN electrode;

Figure 5B illustrates an electron energy loss (EELS) line scan across the device stack illustrated in Figure 5A;

Figure 5C illustrates the XRD pattern of the HZO thin film after post-metal annealing;

Figure 6A illustrates the relationship between polarization and electric field before and after wake-up stress;

Figure 6B illustrates current-voltage DC sweeps of the scaled device before and after wake-up stress;

Figure 7A illustrates the relationship between the resistance of the scaling device and the programming voltage (programming voltage);

FIG. 7B illustrates the relationship between the resistance of the scaling device and the programming voltage for different write pulse widths;

Figure 7C illustrates resistance versus programming voltage for a 4-scale device;

Figure 7D illustrates the stability of the scale device at 4 resistance levels;

Figures 8A to 8F illustrate the variation of conductivity with the number of pulses, thereby illustrating the good linearity of the 4% ozone embodiment of the scale device;

Figure 9 illustrates the relationship between resistance and voltage after different post-metal annealing conditions;

Figures 10A and 10B illustrate the retention of multi-order states over time measured at room temperature; and

Figure 11 illustrates cycling endurance performance.

102: Top electrode

104: Ferroelectric material layer

106: Bottom electrode

108: Substrate

Claims (70)

A ferroelectric tunnel junction comprising: Substrate; a first electrode and a second electrode, wherein a portion of the first electrode or the second electrode has been oxidized to form an interfacial layer; a thin film comprising a crystalline material comprising hafnium oxide and zirconium oxide disposed between the first electrode and the second electrode, wherein the crystalline material exhibits as-deposited ferroelectric behavior; and A voltage source connected to the first electrode or the second electrode. The ferroelectric tunnel junction according to claim 1, wherein the first electrode and the second electrode are independently selected from TiN, W, Ni, Ru, Pt and Al. The ferroelectric tunnel junction according to claim 1 or 2, wherein the first electrode and the second electrode are independently selected from TiN and W. The ferroelectric tunnel junction according to any one of claims 1 to 3, wherein the ferroelectric tunnel junction can be switched between four different resistance states. The ferroelectric tunneling junction according to any one of claims 1 to 4, wherein the resistance state remains stable for at least 10 ³ seconds. The ferroelectric tunnel junction according to any one of claims 1 to 5, which has a memory area between about 1.5 times and about 10 times in the DC domain. The ferroelectric tunnel junction according to any one of claims 1 to 6, which has a memory area between about 2 times and about 5 times. The ferroelectric tunnel junction according to any one of claims 1 to 7, which can exhibit ferroelectric activity. The ferroelectric tunnel junction according to any one of claims 1 to 8, wherein the first electrode comprises tungsten and the second electrode comprises titanium nitride. The ferroelectric tunnel junction according to any one of claims 1 to 9, wherein less than 50% of the total volume of the crystalline material constitutes the non-ferroelectric phase component. A ferroelectric tunnel junction as claimed in any one of claims 1 to 10, wherein less than 40% of the total volume of the crystalline material constitutes a non-ferroelectric phase component. The ferroelectric tunnel junction according to any one of claims 1 to 11, wherein less than 40% of the total volume of the crystalline material constitutes a monoclinic phase component. The ferroelectric tunnel junction according to any one of claims 1 to 12, wherein less than 50% of the total volume of the crystalline material constitutes a monoclinic phase component. The ferroelectric tunnel junction according to any one of claims 1 to 13, wherein (i) greater than 50% of the total volume of the crystalline material is in the ferroelectric phase; (ii) less than 50% of the total volume of the crystalline material constitutes a non-ferroelectric phase component; and (iii) Less than 25% of the total volume of the crystalline material constitutes a monoclinic phase component. The ferroelectric tunnel junction according to any one of claims 1 to 14, wherein the ratio of hafnium oxide to zirconium oxide is between about 1:3 and about 3:1. The ferroelectric tunnel junction of any one of claims 1 to 15, wherein the crystalline material has a carbon content of less than about 6 atomic percent. The ferroelectric tunnel junction according to any one of claims 1 to 16, wherein the crystalline material is derived from one or more metallocene precursors having formula I or formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently selected from C ₁ -C ₆ Straight chain alkyl, C ₁ -C ₆ branched chain alkyl, C ₁ -C ₆ halogenated straight chain alkyl and C ₁ -C ₆ halogenated branched chain alkyl. The ferroelectric tunnel junction according to any one of claims 1 to 17, wherein the crystalline material is derived from one or more metallocene precursors having formula I or formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a C ₁ -C ₆ straight chain alkyl. The ferroelectric tunnel junction according to any one of claims 1 to 18, wherein the crystalline material is derived from one or more metallocene precursors having formula I or formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each methyl. The ferroelectric tunneling junction according to any one of claims 1 to 19, wherein hysteresis and remanence polarization exist when the polarized electric field is measured. The ferroelectric tunnel junction according to any one of claims 1 to 20, wherein the film has a thickness of about 0.2 nm to about 10 nm. The ferroelectric tunnel junction according to any one of claims 1 to 21, wherein the film has a thickness of about 0.2 nm to about 5 nm. A ferroelectric tunnel junction as claimed in any one of claims 1 to 22, wherein the film has a remanence polarization (Pr) greater than 8 μC/cm ² or a total loop opening (total loop opening) greater than 16 μC/cm ² . A method of producing a ferroelectric tunnel junction, comprising: (i) provide the substrate; (ii) depositing a first electrode on the substrate; (iii) depositing a ferroelectric layer on the first electrode at a deposition temperature, the step of depositing the ferroelectric layer comprising: (a) exposing the first electrode to a first precursor that does not decompose at the deposition temperature; (b) exposing the substrate to a first reactive gas; (c) exposing the substrate to a second precursor that does not decompose at the deposition temperature; and (d) exposing the substrate to a second reactive gas, wherein one of the first precursor and the second precursor comprises zirconium, and the other of the first precursor and the second precursor comprises hafnium; and (iv) depositing a second electrode on the ferroelectric layer. The method according to claim 24, further comprising a step of generating an interfacial layer by oxidizing the first electrode before step (iii). The method according to claim 24 or 25, wherein the first reaction gas and the second reaction gas are each independently a gas containing one or more of oxygen, water, hydrogen peroxide and nitrous oxide. The method according to any one of claims 24 to 26, wherein the first reaction gas and the second reaction gas are each independently an oxygen-containing gas, an ozone-containing gas or a water-containing gas. The method of any one of claims 24 to 27, wherein the annealing step is performed at a temperature greater than about 350 degrees Celsius. The method of any one of claims 24 to 28, wherein no process steps occur at a temperature greater than about 400 degrees Celsius. The method of any one of claims 24 to 29, wherein no interfacial layer is deposited between the ferroelectric layer and the first electrode or between the ferroelectric layer and the second electrode. The method of any one of claims 24 to 30, wherein the first gas or the second gas comprises ozone delivered at a volume fraction between about 2% and about 50%. 31. The method of any one of claims 24 to 31, additionally comprising an ozone pulsing step prior to depositing the second electrode. The method of any one of claims 24 to 32, wherein the ozone pulsing step delivers a gas stream comprising between about 2% and about 50% ozone by volume. The method of any one of claims 24 to 33, wherein the deposited crystalline material exhibits remanent magnetic polarization without additional heat treatment. The method of any one of claims 24 to 34, wherein the deposited crystalline material has a residual magnetic polarization (Pr) greater than 8 μC/cm ² or a total loop opening greater than 16 μC/cm ² . The method of any one of claims 24 to 35, wherein the first electrode or the second electrode comprises TiN and the interfacial layer comprises _TiOxNy , where x and _y are integers. The method of any one of claims 24 to 36, wherein the first electrode comprises tungsten and the second electrode comprises titanium nitride. The method according to any one of claims 24 to 37, which additionally comprises at least one purging step. The method according to any one of claims 24 to 38, wherein the first reactive gas and the second reactive gas are different gases. The method according to any one of claims 24 to 39, wherein the first precursor and the second precursor are each independently a precursor of formula I or formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently selected from C ₁ -C ₆ Straight chain alkyl, C ₁ -C ₆ branched chain alkyl, C ₁ -C ₆ halogenated straight chain alkyl and C ₁ -C ₆ halogenated branched chain alkyl. The method according to any one of claims 24 to 40, wherein the first precursor and the second precursor are each independently a precursor of formula I or formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a C ₁ -C ₆ straight chain alkyl. The method according to any one of claims 24 to 41, wherein the first precursor and the second precursor are each independently a precursor of formula I or formula II:

or

Wherein (i) M is selected from Zr and Hf, and (ii) R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ are each methyl. The method according to any one of claims 24 to 42, wherein the method comprises an ALD process. The method according to any one of claims 24 to 43, wherein the method comprises a CVD process. The method of any one of claims 24 to 44, wherein the deposition temperature is between about 200 degrees Celsius and less than about 400 degrees Celsius. The method of any one of claims 24 to 45, wherein the deposition temperature is between about 265 degrees Celsius and less than about 390 degrees Celsius. The method of any one of claims 24 to 46, wherein the deposition temperature is between about 280 degrees Celsius and about 380 degrees Celsius. The method of any one of claims 24 to 47, wherein the deposition temperature is less than about 30 degrees Celsius. The method according to any one of claims 24 to 48, wherein the substrate comprises silicon, germanium, III-V materials, transition metal dichalcogenides, titanium nitride, titanium, tantalum, tantalum nitride, tungsten, platinum , rhodium, molybdenum, cobalt, ruthenium, palladium or their mixtures, or dielectrics such as silicon oxide, silicon nitride, aluminum oxide, titanium oxide. The method of any one of claims 24 to 49, wherein the deposited crystalline material has a thickness of about 0.2 nm and about 20 nm. A method of producing a ferroelectric tunnel junction, comprising: (i) provide the substrate; (ii) depositing a first electrode on the substrate; (iii) pulsing a plasma comprising oxygen and ozone to oxidize a portion of the bottom electrode to form an interfacial layer; (iv) depositing a ferroelectric layer on the first electrode at a deposition temperature, the step of depositing the ferroelectric layer comprising: (a) exposing the first electrode to a first precursor that does not decompose at the deposition temperature; (b) exposing the substrate to a first reactive gas; (c) exposing the substrate to a second precursor that does not decompose at the deposition temperature; and (d) exposing the substrate to a second reactive gas, wherein one of the first precursor and the second precursor comprises zirconium, and the other of the first precursor and the second precursor comprises hafnium; and (v) depositing a second electrode on the ferroelectric layer. The method according to claim 51, wherein the first reaction gas and the second reaction gas are each independently a gas containing one or more of oxygen, water, hydrogen peroxide and nitrous oxide. The method according to claim 51 or 52, wherein the first reaction gas and the second reaction gas are each independently oxygen-containing gas, ozone-containing gas or water-containing gas. The method of any one of claims 51 to 53, wherein the annealing step is performed at a temperature greater than or equal to about 350 degrees Celsius. The method of any one of claims 51 to 54, wherein no process steps occur at a temperature greater than about 400 degrees Celsius. The method of any one of claims 51 to 55, wherein no interfacial layer is deposited between the ferroelectric layer and the first electrode or between the ferroelectric layer and the second electrode. The method of any one of claims 51 to 56, wherein the first gas or the second gas comprises ozone delivered at a volume fraction between about 2% and about 50%. 51. The method of any one of claims 51 to 57, additionally comprising an ozone pulsing step prior to depositing the second electrode. The method of any one of claims 51 to 58, wherein the ozone pulsing step delivers a gas stream comprising between about 2% and about 50% ozone by volume. The method of any one of claims 51 to 59, wherein the deposited crystalline material exhibits remanent magnetic polarization without additional heat treatment. The method of any one of claims 51 to 60, wherein the deposited crystalline material has a residual magnetic polarization (Pr) greater than 8 μC/cm ² or a total loop opening greater than 16 μC/cm ² . The method of any one of claims 51 to 61, _wherein the first electrode comprises TiN and the interfacial layer comprises _TiOxNy , where x and y are integers. The method of any one of claims 51 to 62, wherein the first electrode comprises tungsten (W) and the intermediate layer comprises _WOx , where x is an integer. The method of any one of claims 51 to 63, wherein the first electrode comprises ruthenium (Ru) and the intermediate layer comprises _RuOx , where x is an integer. The method of any one of claims 51 to 64, wherein the first electrode comprises tungsten and the second electrode comprises titanium nitride. The method of any one of claims 51 to 65, wherein the annealing step is performed at a temperature lower than or equal to about 400 degrees Celsius. The ferroelectric tunnel junction according to any one of claims ₁ to 23 or the method according to any one of claims 24 to 66, wherein the film comprises Hf _x Zr doped with La, Y, Gd or Sr _-x O ₂ or HfO ₂ . An interleaved memory array comprising the ferroelectric tunnel junction according to any one of claims 1 to 23 or the ferroelectric tunnel junction produced by the method according to any one of claims 24 to 66, the The ferroelectric tunnel junction includes a memory unit cell. A neuromorphic computing chip comprising the ferroelectric tunneling junction according to any one of claims 1 to 23, wherein the ferroelectric tunneling junction is a synapse device. The ferroelectric tunnel junction according to any one of claims 1 to 23, which has a critical dimension of about 300 nm or less.

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